Lightweight electromagnetic relay

ABSTRACT

A lightweight hermetically sealed electromagnetic relay has an electromagnet, an armature, and a contact assembly. An isolation barrier is interposed between the electromagnet assembly and the armature and contact assemblies and is arranged to support each of the assemblies. A transparent cover is bonded to the isolation barrier and protects the electrical contacts against external contamination from the operating environment as well as against internal contamination from impurities emitted by the coil insulative material.

[22] Filed:

[52] U.S.Cl

United States Patent Schroeder [54] LIGHTWEIGHT ELECTROMAGNETIC RELAY [72] Inventor:

[73] Assignee:

Theodore C. Schroeder, Greentree, Pa.

Westinghouse Air Brake Company, Swissvale, Pa.

June 3, 1970 [21] App1.No.: 43,114

.335/202 [51] Int. Cl. ..H01h 9/02 [58] Field of Search ..335/202, 125, 187

[.56] References Cited UNITED STATES PATENTS 3,516,035 6/ 1970 Josenhans ..'...335/202 51 June 6,1972

Adams ..335/l25 Mathison et al. ..335/202 Primary Examiner-Harold Broome Attorney-H. A. Williamson, A. G. Williamson, Jr. and J. B. Sotak [57] ABSTRACT A lightweight hermetically sealed electromagnetic relay has an' electromagnet, an armature, and a contact assembly. An isolation barrier is interposed between the electromagnet assembly and the annature and contact assemblies and is arranged to support each of the assemblies. A transparent cover is bonded to the isolation barrier and protects the electrical contacts against external contamination from the operating environment as well as against internal contamination from impurities emitted by the coil insulative material.

' 16 Claim, 3 Drawing Figures LIGHTWEIGHT ELECTROMAGNETIC RELAY My invention relates to a miniature electromagnetic relay and more particularly to a balanced armature type of switching relay which is hennetically sealed against environmental contamination and includes an isolation barrier between the electromagnetic coil structure and the electrical contact structure thereby eliminating the possibility of contact fouling due to impurities emitted by the coil insulating material.

At the present time, there is an ever increasing need and demand for improved electromagnetic relays which have the attributes of being low in cost, simple in construction, reliable in operation, durable in use and efficient in service. In addition, it is desirable that the relays have a low power requirement and yet have a high contact current carrying quality. These characteristics are extremely difficult to attain in conventional size relays and are next to impossible to achieve in miniature size relays. Previous attempts to succeed were hampered not only by the minute size of these lightweight relays but also by the millieu in which these relays are required to operate. The small size requires extremely close tolerances and allowances which are only attainable with expertise on the part of the craftsman and by precision on the part of the machinery. Once this scientific accuracy is met, the assembled relays are required to function properly under one of the most adverse operating conditions. In aircraft, rocket and satellite applications, the miniature relays are subject to a great range of pressure and temperature changes as well as to extreme gravitational and vibrational forces. In the past, the pressure and temperature variations resulted in numerous failures of the relays in that contaminants emitted by the electrical insulating material could cause fouling of the electrical contacts. In some cases, the gravitational and vibrational forces also caused the.

prior art relays to operate in an erratic manner in that an unstable armature could cause inadvertent opening and closing of the electrical contacts. Thus, an acceptable miniature relay must be small in size, must be made with precision and must be capable of operating satisfactorily under all adverse physical conditions.

Accordingly, is is an object of my invention to provide a new and improved miniature relay which overcomes the above-mentioned deficiencies.

Another object of my invention is to provide a unique relay having electrical switching contacts which are hermetically sealed against external as well as internal contamination.

A further object of my invention is to provide an improved lightweight electromagnetic relay having a balanced armature structure and electrical contact structure each of which is separated by an isolation barrier from the electromagnetic coil structure.

Yet another object of my invention is to provide a unique miniature relay having a barrier and a transparent cover for hermetically sealing the electrical switching contacts against contamination.

Yet a further object of my invention is to provide a lightweight relay having a intermediate supporting wall for holding the magnetic coil assembly as well as for sustaining the magnetic armature assembly and the electrical contact assembly.

Still another object of my invention is to provide an improved lightweight hermetically sealed electromagnetic relay having a balanced armature for actuating a plurality of singlepole double-throw contacts.

Still a further object of my invention is to provide a dual-in- Still yet a further object of my invention is to provide a new and improved miniature electromagnetic relay which is low in cost, simple in construction, reliable in operation, durable in use and efficient in service.

In general, my invention relates to a hermetically sealed miniature relay including an electromagnetic coil assembly, a balanced armature assembly and an electrical contact switching assembly. An intermediate isolation barrier is interposed between the electromagnetic coil assembly and the balanced armature and electrical contact switching assemblies. The electromagnetic coil assembly includes an electrical coil, a core and a pair of pole pieces which are supported by the isolation barrier. The pole pieces include pole faces pro- 1 5 jecting beyond one side of the isolation barrier. The balanced armature assembly includes a pivotal shaft carried by the isolation barrier for centrally pivoting the balanced armature. A biasing spring normally urges the balanced armature to a retracted position which is away from the pole faces and against a stop member. A plurality of elongated circuit pins arranged in a dual-in-line fashion extend through the isolation barrier. The electrical contact switching assembly includes a plurality of movable and stationary spring contacts each of which is secured to one end of separate ones of the elongated circuit pins. A plurality of actuators are carried by the balanced armature for opening and closing the movable and stationary spring contacts in response to the energization and deenergization of the electrical coil. A transparent cover is bonded to the isolation barrier and hermetically encloses the armature and contact assemblies so that the electrical spring contacts are prevented from being fouled by environmental contaminants or by impurities emitted by the insulating material associated with the electromagnetic coil assembly.

For a more complete understanding of my invention as well as realizing other objects and advantages therefrom, reference is made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a top plan view of the electromagnetic relay of the present invention with a portion of the cover broken away to more clearly illustrate the details thereof.

FIG. 2 is a sectional view taken along lines II-II of FIG. 1 with a portion of the coil insulation removed.

FIG. 3 is an end sectional view of the electromagnetic relay of FIG. 1 with a slight modification thereof.

Referring now to the drawings, there is shown a lightweight hermetically sealed relay which is generally characterized by the numeral 1. The miniature electromagnetic relay 1 essentially consists of three separate or individual sub-assemblies, namely a magnetic coil assembly or structure 2, a magnetic armature assembly or structure 3, and an electrical contact assembly or structure 4.

As shown, in FIG. 2, the magnetic coil assembly comprises an electromagnet having an electrical coil and a magnetic circuit. The electrical coil which is generally characterized by numeral 7 includes a multi-turn winding 8 wound on a cylindrical bobbin 9 molded of suitable insulating material. The fine wire forming the energizing winding 8 is generally varnished during the drawing process in order to provide the necessary insulation between the turns. The coil winding 8 is preferably surrounded with an insulative cover or tape 11 which is wrapped around the entire outer outer surface thereof. As shown, the terminals or leads of winding 8 extend from each end of the coil 7 and are connected to lead wires 12 and 13. The leads 12 and 13 are preferably covered by an insulative spaghetti or tubing 14 and 15, respectively. The free ends of the leads l2 and 13 are electrically connected, such as by being soldered, to appropriate terminal pins or wires for selective connection to a suitable source of energizing voltage, as is conventional.

It has been established that under extreme environmental conditions, such as under very high temperatures and pressures, certain contaminants or pollutants are released by insulative material which can materially affect the operation of the relay and in some cases cause a complete failure thereof. In

the past, these emitted contaminants imparied the switching reliability of the relay by allowing carbon particles to be formed between the switching contacts. Also, the pollutants detracted from the switching ability of the relay by causing oxidation to form on the contact points which obviously results in poor electrical contact. It has also been found that certain lubricants employed in the wire drawing process are also capable of fouling contact switching operations of the relay under the above conditions. While it is common practice to cure or bake the electrical coil in an oven prior to its assembly as an electromagnet such a heating operation does not entirely relieve the contamination problem. Thus, other methods and practices must be employed to overcome this adverse contamination problem. It has been found that complete isolation between the electrical contacts and the contaminating producing material completely alleviates the fouling problem yet effectively allows for proper relay operation.

Thus, a flat rectangular isolation wall or barrier is interposed between the contaminant producing insulative material and. the electrical switching contacts of the relay 1. The isolation barrier 15 is preferably constructed of suitable insulating material, such as, glass or some other type of ceramic material. As will be presently described, insulation barrier 15 not only is employed for its isolation and insulating characteristics but also is utilized as a mounting and supporting member for carrying the various sub-assemblies and parts which form the electromagnetic relay 1. It will be noted that the magnetic circuit of the electromagnetic relay 1 includes a cylindrical core member 16 and a pair of upstanding pole pieces 17 and 18. The core member 16 passes through the center opening in bobbin 9 and extends slightly beyond both ends of bobbin 9. The pair of pole pieces 17 and 18 are jointed to ends of the core member 16 by stakingor otherwise. As shown, the pole pieces 17 and 18 projected through and are molded within the insulative barrier 15. Thus, the electromagnetic structure 2 is securely fastened to and supported by the isolation barrier 15. Each of the pole pieces 17 and 18 is provided with a flat pole face 17a and 180, respectively, which may be machined or otherwise formed on upper pole face to cooperate with portions of a movable armature, as will be described presently.

As shown, a plurality of elongated terminal pins 20 through 35 are also molded within and supported by the insulative barrier 15. Each of the terminal pins has a portion extending on opposite sides of the barrier 15 so that exposed portions are available for the-switching contacts as well as for connection tothe associated external circuits.

In viewing FIGS. 1 and 2, it will be seen that a pivotal shaft 40 is centrally located on the upper side of the barrier 15. Like the conducting pins and the pole pieces, the lower end of nonmagnetic shaft 40 is embedded and bonded within the body of the insulative barrier 15. An armature, somewhat Z-shaped in form, is received and is pivotally mounted on the non-magnetic shaft 40. As shown in FIG. 2, the lower surface of armature 41 is slightly spaced above the upper surface of the barrier 15 by abutting against annular shoulder 42 formed on the enlarged portion of shaft 40. A split retaining ring or the like cooperates with an annular groove (not characterized) provided in the upper end of shaft 40 and maintains the armature in proper position. Thus, the magnetic armature 41 is rotatably mounted upon shaft 40 between shoulder 42 and the retaining ring 43. A U-shaped biasing spring 44 normally urges the adjacent surfaces of the armature 41 away from the flat pole faces 17a and 180. As shown, the bight portion of the U- shaped biasing spring 44 is preferably seated into an annular groove (not characterized) formed in the peripheral edge of shoulder 42 slightly above the upper surface of the insulative barrier 15. It will be noted that the free end of one of the legs ofthe spring 44 includes an eyelet (not characterized) which encompasses a pin 39 embedded in and extending from upper surface of the insulative barrier 15. The free end of the other leg of the U-shaped spring 44 also includes an eyelet (not characterized) which surrounds a pin 38 depending on annature 41. Thus, the armature 41 is normally biased to its retracted position, as shown in FIG. 1, in which the armature 41 engages a stop member 45 embedded in the insulative barrier 15. Thus as previously mentioned, the insulative barrier 15 not only mechanically supports the various elements but also provides necessary electrical insulation between the elongated terminal pins 21 through 35.

A pair of flat strap-like actuators 46 and 47 are secured, such as by welding to the opposite sides of the armature 41. As shown in FIG. 1, the free ends of the inclined portions of the actuator 46 are each provided with beads 48 and 49 while the free ends of the inclined portions of actuator 47 are provided with beads 50 and 51. Each of the beads is formed of non-conducting material, such as glass or the like. The non-conducting beads 48 through 51 cooperate with a plurality of spring-like movable electrical switching contacts which are employed to establish and interrupt various circuits controlled by the relay 1. As shown, the movable and stationary electrical contacts takes the form of four single-pole double-throw switches.

Thus, this type of assembly switch configuration includes four movable contacts 55, 56, 57, and 58 and eight stationary contacts 60 through 67. It will be noted that each of the contacts is bent into a substantially L-shaped form. The contacts are constructed of a suitable high conductive strap-like material, such as beryllium copper, which may have the contact surfaces silver plated to improve their electrical contact characteristics. Each of the L-shaped contacts has one leg secured such as by being welded to the upper projecting portion of the various terminal pins. For example, the contacts 61, 60, 55, 56, 63, 62, 64, 57, 58, 66, and 67 are securely fastened to terminal pins 21, 22, 23, 24, 25, 26, 29, 30, 31, 32, 33 and 34, respectively. As shown, the free ends of the other leg of stationary contacts 60 and 61 are bent in such a fashion that a substantially large contact area is provided. The free ends of the stationary contacts are juxtaposed and spaced apart a given amount so that the free end of the movable contact may be interposed therebetween and may be moved into engagement with either one of the stationary contacts. For example, the free end of movable contact 55 is interposed between the stationary contacts 60-61. Similarly, the remaining stationary contact pairs 62-63, 64-65, and 66-67 have their free ends suitably bent and spaced apart the approprite-amount toallow the .movable contacts 56, 57, and 58 to be interposed therebetween. As previously mentioned, the free ends of the contacts are preferably silver plated to improve their electrical characteristics, and it will be appreciated that the contacting surface area may be varied simply by modifying the bent por tions of the stationary contacts. For example, the surface contact area of stationary contact elements may be increased by extending the length of the hooks. Such a lengthening of the hook not only increases the lateral dimension of the hook but also augments the orthogonal dimension so that an appreciable surface contact area may be realized. Thus, it will be noted that by utilizing a strap-like contact material a relatively large contact surface area may be realized so that the relay may have a greater current carrying capacity. Further, it will be noted that all of the spring contacts of each of the four singlepole double-throw switches are readily accessible so that installation of the contacts and any adjustments during manufacturing are relatively easy to perform. Similarly, the inclined actuator arms carrying beads 48, 49, 50 and 51 are readily accessible and may be easily adjusted in relation to the movable contacts 55, 56, 57 and 58, respectively.

After the necessary adjustments have been made the entire contact and armature assemblies may be enclosed within a transparent cover 70 which embraces and tightly fits against the upper peripheral edge of the insulating barrier 15. That is, the rim 71 of cover 70 is suitably bonded to the upper surface of the barrier 15 so that the internal elements are hermetically sealed against the atmosphere of the environment. If desired the contact and armature chamber may be evacuated and filled with inert gas in order to reduce the possibility of contact corrosion. ln viewing FIG. 2, it will be noted that the electromagnet assembly 2 is also enclosed within an insulative cover 72 which may be bonded to the lower surface of the barrier 15. It will be appreciated that the lower cover 72 must be provided with a plurality of appropriately spaced dual-in-line openings for accommodating the terminal pins through 35 so that the connections may be made to the externally controlled circuits. I

In viewing FIG. 3, it will be noted that all the relay components or elements are the same except that the lower plastic cover has been replaced by insulative potting material 75 which protects the electromagnetic assembly 2 against external damage. That is, the electromagnetic assembly 2 is simply encapsulated within potting material 75 which is bonded to the lower surface of the insulating barrier 15. The potting material 75 not only protects the electromagnetic against damage but also adds reinforcement to the terminal pins since the insulative barrier and the potting material embrace these pins along a substantial portion of their length.

In operation the electromagnetic relay I normally assumes a position as shown in FIG. 1. That is, when the coil 7 of the electromagnet 2 is not energized, the armature 41 is normally urged by spring 44 to the retracted position where the left end of armature 41 engages the stop member 45. Under this condition, the glass beads 48 and 51 of actuators 46 and 47 normally urge the movable contacts 55 and 58, respectively, into engagement with stationary contacts 60 and 66. Thus, an external circuit may be completed from terminal pin 22 through the stationary contacts 60, and, movable contact 55 to terminal pin 23. In a similar manner, 'an external circuit may be completed from terminal pin 32 through stationary contact 66 through movable contact 58 to terminal pin 33. Under this deenergized condition, the glass beads 49 and 50 are arranged such as to permit the normal resiliency of the spring contacts 56 and 57 to move them against the stationary contacts 62 and 64, respectively. Thus, an external circuit may be completed from pin 24, through movable contact 56, through stationary contact 62 and to terminal pin 26. Similarly,'an external circuit may be completed from pin 29, through stationary contact 64, through movable contact 57 and to pin 31. The remaining stationary contacts of the four single-pole doublethrow switches are not engaged so that the external circuits common to pins 21, 25, 29 and 34 are open-circuited.

Let us now assume that switching operation is desired so that electrical power is applied across terminal pins 20 and 27. Application of a voltage supply across pins 20 and 27 causes the coil 7 to become energized so that a magnetic field is set up in the electromagnet 2. The magnetic field influences the armature 41 so that it is displaced angularly in a counterclockwise direction as viewed in FIG. 1. As the armature 41 quickly moves against the pole faces 17a and 18a the actuators are moved therewith and the glass beads shift the movable contacts 55, 56, 57 and 58 to their opposite positions. The glass bead 48 is effectively withdrawn so that movable contact 55 breaks with stationary contact 60 and makes with contact 61. Similarly, glass bead 51 is effectively withdrawn thereby allowing movable contact 58 to break with stationary contact 66 and to make with contact 67. The glass bead 49 causes the movable contact 56 to break with contact 62 and to make with contact 63. Similarly, the glass bead 50 causes the movable contact 57 to break with stationary contact 64 and to make with stationary contact 65. Thus the four single-pole doublethrow switches each undergoes a conductive change of state. Now when the voltage source is removed from terminal pins 20 and 27, the electromagnetic coil becomes deenergized so that the armature is quickly returned to its retracted position by biasing spring 44. Thus, the relay 1 will again assume a position as shown in FIG. 1. 1

As previously mentioned, the effects of vibration, shock and gravity are appreciably reduced by centrally pivoting the armature 41 so that a balancing action of these forces results. Accordingly, there is little, if any, change or likelihood that the actuators will cause any unwanted movement which can open or close the electrical contacts. Further, as mentioned above the central disposition and arrangement of armature assembly allows sufficient space to be available for initially adjusting the contacts and actuators with relative ease. In addition, each of the four switches is fully exposed so that the contact may be visually inspected for wear and erosion. Also, it will be appreciated that no problem is encountered with the alignment of the magnetic pole faces with respect to the adjacent portion of the armature.

In addition to acting as a support member, the dielectric barrier 15 operates as an insulator for isolation of the electrical contacts and the terminal pins.

Further, while my invention has been described in regard to a preferred embodiment, it is readily understood that other changes may be made by those skilled in the art without departing from the spirit and scope of my invention. For example, while the invention that has been described in regard to a dual-in-line package, it is understood that other types of relays and pin arrangements may be employed in'practicing my invention. Therefore, it is understood that the foregoing description is only illustrative of my invention and is not intended that the invention be limited thereto. It is, therefore, contemplated by the appended claims to cover all variations, alterations and modifications as fall within the spirit and scope of the invention.

Having thus described my invention, what I claim is:

l. A hermetically sealed electromagnetic relay comprising, an electromagnet assembly, a magnetic armature assembly and an electrical contact assembly, an intermediate insulative barrier separating said electromagnet assembly from said mag netic armature and said electrical contact assemblies, said electromagnet assembly including a coil, a core and a pair of pole pieces which are supported by said barrier, said pole pieces having pole faces protruding from one side of said barrier, said magnetic armature assembly is pivoted on a shaft which is supported on said one side of said barrier, said magnetic armature assembly includes portions disposed adjacent said pole faces, said electrical contact assembly includes a plurality of movable and stationary contacts which are mounted on said one side of said barrier, said movable contacts are adapted to be moved into and out of engagement with said stationary contacts by said magnetic armature as said coil is energized and deenergized.

2. An electromagnetic relay as defined in claim 1, wherein said magnetic armature is pivoted about its center of gravity so that externally generated forces are equalized.

3. An electromagnetic relay as defined in claim 1, wherein said magnetic armature is pivoted about an axis orthogonal to the plane of said one side of said barrier and includes a plurality of actuators which move said movable contacts parallel to the plane of said one side of said barrier. I

4. An electromagnetic relay as defined in claim 3, wherein a transparent cover is secured to said one side of said barrier so that the physical condition of said movable and said stationary contacts may be readily ascertained.

5. An electromagnetic relay as defined in claim 1, wherein a plurality of conductor pins extend through said barrier having portions projecting beyond said one side of said barrier to which said movable and said stationary contacts are attached.

6. An electromagnetic relay as defined in claim 2, wherein a return spring is connected between said magnetic armature and said barrier for normally biasing said magnetic armature to a neutral position.

7. An electromagnetic relay as defined in claim 5, wherein the pair of terminal ends of said coil are connected to respective ones of said plurality of conductor pins at a point located on the other side of said barrier.

8. An electromagnetic'relay as defined in claim 1, wherein said intermediate barrier is constructed of an insulative material.

9. An electromagnetic relay as defined in claim 5, wherein said electromagnet assembly is enclosed within a protective housing.

10. An electromagnetic relay as defined in claim 9, wherein said plurality of conductor pins extend beyond the outer surface of said protective housing.

l 1. An electromagnetic relay as defined in claim 6, wherein a stop member is carried by said barrier for engaging said magnetic armature and limiting the return movement of said return spring.

12. A miniature electromagnetic relay comprising: an electromagnet, a balanced armature and a plurality of movable and stationary contacts, said electromagnet including an insulated coil, a core and a pair of pole pieces, an insulative dividing wall having said pole pieces extending therethrough, said dividing wall separating said insulated coil from said balanced armature and said movable and stationary contacts, a plurality of conductor wires extending through and sealed in said dividing wall, each of said plurality of movable and stationary contacts attached to separate ones of said plurality of conducting terminals, a pivot pin is carried by said dividing wall for pivotally supporting said balanced armature, actuators operated by said balanced armature for opening and closing said movable and stationary contacts whenever said coil is energized and deenergized, a cover attached to said dividing wall and hermetically sealing said contacts against contamination, and a shield encasing said insulted coil.

13. A miniature electromagnetic relay as defined in claim 12, wherein said cover is transparent in order to facilitate inspection of operation.

14. A miniature electromagnetic relay as defined in claim 12, wherein said plurality of movable and stationary contacts take the form of four single-pole double-throw switches.

15. A miniature electromagnetic relay as defined in claim 12, wherein said actuators are welded to opposite sides of said balanced armature and include a nonconductive ball at the outer extremity thereof which contact said movable contacts.

16. A miniature electromagnetic relay as defined in claim balanced armature to a neutral position. 

1. A hermetically sealed electromagnetic relay comprising, an electromagnet assembly, a magNetic armature assembly and an electrical contact assembly, an intermediate insulative barrier separating said electromagnet assembly from said magnetic armature and said electrical contact assemblies, said electromagnet assembly including a coil, a core and a pair of pole pieces which are supported by said barrier, said pole pieces having pole faces protruding from one side of said barrier, said magnetic armature assembly is pivoted on a shaft which is supported on said one side of said barrier, said magnetic armature assembly includes portions disposed adjacent said pole faces, said electrical contact assembly includes a plurality of movable and stationary contacts which are mounted on said one side of said barrier, said movable contacts are adapted to be moved into and out of engagement with said stationary contacts by said magnetic armature as said coil is energized and deenergized.
 2. An electromagnetic relay as defined in claim 1, wherein said magnetic armature is pivoted about its center of gravity so that externally generated forces are equalized.
 3. An electromagnetic relay as defined in claim 1, wherein said magnetic armature is pivoted about an axis orthogonal to the plane of said one side of said barrier and includes a plurality of actuators which move said movable contacts parallel to the plane of said one side of said barrier.
 4. An electromagnetic relay as defined in claim 3, wherein a transparent cover is secured to said one side of said barrier so that the physical condition of said movable and said stationary contacts may be readily ascertained.
 5. An electromagnetic relay as defined in claim 1, wherein a plurality of conductor pins extend through said barrier having portions projecting beyond said one side of said barrier to which said movable and said stationary contacts are attached.
 6. An electromagnetic relay as defined in claim 2, wherein a return spring is connected between said magnetic armature and said barrier for normally biasing said magnetic armature to a neutral position.
 7. An electromagnetic relay as defined in claim 5, wherein the pair of terminal ends of said coil are connected to respective ones of said plurality of conductor pins at a point located on the other side of said barrier.
 8. An electromagnetic relay as defined in claim 1, wherein said intermediate barrier is constructed of an insulative material.
 9. An electromagnetic relay as defined in claim 5, wherein said electromagnet assembly is enclosed within a protective housing.
 10. An electromagnetic relay as defined in claim 9, wherein said plurality of conductor pins extend beyond the outer surface of said protective housing.
 11. An electromagnetic relay as defined in claim 6, wherein a stop member is carried by said barrier for engaging said magnetic armature and limiting the return movement of said return spring.
 12. A miniature electromagnetic relay comprising: an electromagnet, a balanced armature and a plurality of movable and stationary contacts, said electromagnet including an insulated coil, a core and a pair of pole pieces, an insulative dividing wall having said pole pieces extending therethrough, said dividing wall separating said insulated coil from said balanced armature and said movable and stationary contacts, a plurality of conductor wires extending through and sealed in said dividing wall, each of said plurality of movable and stationary contacts attached to separate ones of said plurality of conducting terminals, a pivot pin is carried by said dividing wall for pivotally supporting said balanced armature, actuators operated by said balanced armature for opening and closing said movable and stationary contacts whenever said coil is energized and deenergized, a cover attached to said dividing wall and hermetically sealing said contacts against contamination, and a shield encasing said insulted coil.
 13. A miniature electromagnetic relay as defined in claim 12, wherein said cover is transparent in order to facilitate inspection of oPeration.
 14. A miniature electromagnetic relay as defined in claim 12, wherein said plurality of movable and stationary contacts take the form of four single-pole double-throw switches.
 15. A miniature electromagnetic relay as defined in claim 12, wherein said actuators are welded to opposite sides of said balanced armature and include a nonconductive ball at the outer extremity thereof which contact said movable contacts.
 16. A miniature electromagnetic relay as defined in claim 12, wherein a U-shaped return spring normally urges said balanced armature to a neutral position. 